LUIGI GALVANI

De viribus electricitatis in motu muscolari.
Commentarius

Commentary on the effects of electricity on muscolar motion

[Printed for the first Galvanis Commentary on effects of electricity on muscular motion, with notes and critical introduction by I. Bernard Cohen, Norwalk (Conn.), Burndy Library, 1953.

PART I

THE EFFECTS OF ARTIFICIAL ELECTRIClTY ON MUSCULAR MOTION

[3] Since I wish to bring to a degree of usefulnessthose facts which came to be revealed about nerves and muscles through many experiments involving considerable endeavor, whereby their hidden properties may possibly be revealed and we maybe able to treat their ailments with more safety, there seems no better way for fulfilling this desire than by publishing these discoveries at length (such as they are). For after reading of our experiments, learned and distinguished scholars wilI not only be able to develop them through their own studies and investigations, but even to carry out other experiments which we may have attempted but perhaps could nor bring to conclusion..

It was likewise my wish to publish a treatise, even though it were far from being a finished and complete work (something I perhaps never could have done), one at least which was not crude and only half begun; but since I realized that Ihad neither the time, leisure, nor ingenuity to accomplish this, I preferred to sacrifice this clearly reasonable wish of mine to expediency.

I thought my efforts would be rewarded, therefore, if I presented a brief and accurate account of the discoveries in the same order of circumstance that chance and fortune in part brought to me, and diligence and attentiveness in part revealed. I hoped to do this not only that more might not be attributed to me than to fortune, nor to fortune than to me, hut that we might either light the way for those who have wished to embark upon this same course of experiment or that, in any event, we might satisfy the honest curiosity of scholars who are interested in the source or origin of things which embody an innate and unusual element.

Now, Ishall occasionally add inferences, conjectures, and hypotheses to the account of the experiment with the primary purpose of paving the way for the undertaking of new experiments. But if, in this way we are unable to arrive at the truth, we will at least have opened a new approach to it.

The course of the work has progressed in the following way. I dissected a frog and prepared it as in Fig. [omega], Tab. 1. Having in mind other things, I placed the frog on the same table as an electrical machine,Fig. 1, Tab. 1, so that the animal was completely separated from and removed at a

considerable distance from the machine's conductor.When one of my assistants by chance lightly applied the point of a scalpel to the inner crural nerves, DD, of the frog, suddenly all the muscles of the limbs were seen so to contract that they appeared to have fallen into violent tonic convulsions. Another assistant who was present when we were performing electrical experiments thought he observed that this phenomenon occurred when a spark was discharged from the conductor of the electrical machine, Fig. 1, B. Marvelling at this, he immediately brought the unusual phenomenon to my attention when I was completely engrossed and contemplating other things. Hereupon I became extremely enthusiastic and eager to repear the experiment so as to clarify the obscure phenomenon and make it known. I myself, therefore, applied the point of the scalpel first to one then to the other crural nerve, while at the same time some one of the assistants produced a spark; the phenomenon repeated itself in precisely the same manner as before. Violent contractions were induced in the individual muscles of the limbs and the prepared animal reacted just as though it were seized with tetanus at the very moment when the sparks were discharged.

I was fearful, however, that these movements arose from the contact of the point, which might act as a stimulus, rather than from the spark. Consequently I touched the same nerves again in other frogs with the point in a similar manner, and exerted even greater pressure, but absolutely no movements were seen unless someone produced a spark at the same time. Thus I formed the idea that perhaps in order to produce this phenomenon there were required the simultaneous contact of some body and the emission of a spark. I therefore again applied the edge of the scalpel to the nerves and held it motionless. I did this at one time when sparks were discharged and at another when the electrical machine was completely quiet. The phenomenon occurred, however, only as often as a spark was produced.

We repeated the experiments with the same scalpel and found, to our astonishment, that at times, when a spark was produced, the aforementioned movements were evident, and at others, they were absent.

[5] Excited by the novelty of the phenomenon, we began to make tests and experiments of various kinds, but always using the same scalpel, in order to understand, if possible, the reasons for this unexpected difference. Nor was this additional diligence without its reward, for we discovered that the answer to the problem lay in the part of the scalpel we held in our fingers. Since the scalpel had a bone handle, we found that when this handle was held in the hand, no movements were produced at the discharge of a spark. They did occur, however, when the fingers touched the metal blade or the iron nails that secured the blade of the instrument.

Now since dry bones exhibit an idioelectric (or non-conducting) nature, while a metal blade and iron nails exhibit an anelectric (or non-conducting) nature,as they say, we began to suspect that perhaps when we held the bone handle in our fingers, there was no way for the electric fluidto flow (by whatever means) into the frog, but when we took hold of the blade or nails and brought them in contact with the frog, a path was opened.

To place this conclusion beyond all doubt, therefore, we used at one time a thin glass cylinder, Fig. 2, H, wiped clean of all moisture and fine dust, in place of the scalpel, and at another, one of iron, G. At the time when a spark was discharged, we were not only touching the crural nerves with the glass rod, but were actually rubbing them. Our efforts were unsuccessful, however, since the phenomenon did not reappear although numerous strong sparks were discharged from the conductor of the electrical machine at dose range to the animal. On the other hand, when the iron rod was only lightly applied to the same nerves and when only weak sparks were emitted, the phenomenon once again occurred.

This clearly confirmed what we had suspected to be true, namely that the contact of a conducting substance with the nerves is necessary to produce the phenomenon. But in this experiment use had been made of both the substance, by which the nerves were touched and the man who touched them; so we applied the iron rod, G, to the same nerves but did not hold it in our hands. In this way we hoped to ascertain whether the phenomenon should be ascribed to the man and the iron rod together or to the latter alone. When the experiment was made in this way, no movement of the muscles occurred when the spark was emitted. In place of the cylinder, therefore, we used a very long wire, Fig. 2, KK, in order to see whether or not this could somehow compensate for the absence of the man. And behold! the muscles contracted when the sparks were discharged.

[6] From these observations it became clear to us that not only was a conducting substance that touched the nerves required to produce the phenomenon, but one also of determined size and length. Hereafter, for the sake of clearness rather than brevity, allow us to call a conducting substance of this sort a nerve-conductor.

Now, to the end of this conductor, we attached a small hook which was fastened to the frog's spinal cord, Fig. 2. At one time we placed the frog near the electrical machine and at another we arranged

its conductor in such a manner that now the frog was near to the electrical machine and now removed at a distance from it. Because at one time the feet and at another the prepared nerves were turned towards the electrical machine, the latter now had the conductor before it and now behind. No matter what the arrangement was, contractions of equal intensity were always produced.

We investigated, moreover, whether the phenomenon took place in prepared animals even when the experiment was performed at a distance from the electrical machine and very long nerve-conductors were employed. We were able to ascertain that when an iron wire of one hundred and more ellsin length was attached to the frog, muscular contractions occurred at the emission of a spark, even though the distance from the electrical machine was very great. We carried out the experiment in the following way. We suspended an iron wire, Fig. 3, FF, by silk threads and thereby insulated it, as the natural philosophers say. Then we fastened one end by a silk thread to a nail, F, driven into the wall; the other end we carried away from the electrical machine through various rooms as far as the wire reached. To the latter at point, C, we joined another iron wire, B, from whose end a frog was suspended. For the sake of convenience, we enclosed the frog in a glass jar, A, whose bottom was covered with some conducting material, e.g. water or very small lead shot of the kind used by hunters (the latter brought about the best experimental results). When a spark was discharged from the conductor of the electrical machine, the limbs of the prepared frog moved, even at so great a distance - which was truly extraordinary - and almost jumped. The same phenomenon occurred when the frog was removed from the glass jar and was hung in a similar manner from the conductor, EE. This happened much more quickly if some conducting body, which was in contact with the earth, were fastened to the feet of the animal.

Since these results had been observed with an insulated conductor, we next investigated what would happen with one that was not insulated.

We attached the iron wire, EE, therefore, to the various hinges of the doors of the rooms of my house, six in number. All things [7] were arranged as in the previous experiment. When a spark was discharged, only small contractions were produced in the prepared frog, but nonetheless there were some.

Having made these observations, we now wished to find out whether the force of this electricity moved and spread out equally in all directions in a circle, as seemed reasonable. To this end different nerve-conductors were arranged at some distance from, and in a circle around, the conductor of the electrical machine. A prepared frog was fastened on each of these. When a spark was produced, what a gratiyng sight! The individual frogs time and again moved in unison, particularly when a conducting body was attached to their feet, as in the preceding experiment. The reaction was particularly strong when the conducting body was grounded, a thing easily accompilshed by either fastening a long metal wire to the individual feet of the frogs or by holding them in the fingers.

Consequently, when we became aware of the usefulness, or even the necessity of fastening conducting bodies to the feet of the animals, we were eager to attempt new experiments embracing this problem. Once these were performed, it became clear that the conducting bodies which we attached to the muscles to bring about contractions either were at times sufficient by themselves to produce this effect without nerve-conductors, or, at any rate, made no small contribution to the effect. Moreover, the larger the conducting bodies were and the more they were possessed of a strong conducting power, the greater were the contractions, particularly if the conductors were in contact with the earth. They were at least as effective as those conductors which we were accustomed to attach to the nerves.

Hereafter we shall call these conducting bodies muscle-conductors to distinguish them conveniently from the so-called nerve-conductors.

Now, in an experiment where the nerve-conductor, extended to some distance from the electrical machine, is intercepted by some non-conducting body which was intentionally made, as it were, in part of a conducting substance, like metal, and in part of anon-conducting substance, like glass, resin, or silk, we see no contractions following the production of a spark although we have attached conductors to the individual muscles. An example of this would be if conductor, Fig. 3, B, were not joined to conductor, EE, at point, C, bur were suspended by a silk loop, D. This is new and indubitable evidence that electricity is dìssipated through conductors of this kind.

We also carried out the experiment with the conductor not only intercepted by a non-conductor but completely interrupted, [8] and with the ends of the interrupted conductor placed as dose as possible to one another. The phenomenon of contractions was completely absent.

And again, in another way we sought to intercept the free flowing of electricity through the conductor. We placed a prepared animal on a non-conducting surface. We did not join its nerve-conductor as before with either the nerves or the spinal cord, but arranged it on the same surface in such a way that its end was several lines and occasionally even a thumb's width away from the nerves or spinal cord. When a spark was produced, contractions occurred. They also occurred when the limbs were placed on a conducting surface and the nerves on a non-conducting surface with the nerve-conductor the same distance away. This was also the case when the nerves were held up in the fingers with just a short nerve-conductor attached, or a long one, whereby the animal was either near to or far from the electrical machine. The contractions were completely absent, however, if the nerves with their conductor separated from them, as in the foregoing experiments, were placed on a conducting surface.

We did not omit investigating whether this electric force, of whatever kind it might be, also excited those contractions which we have often mentioned, when it was only flowing freely through the substance of the conductors, and not the surface. Hence we covered and completely enveloped-with a non-conducting substance, such as common wax, sealing-wax, or pitch except for the ends-the iron wire which served as a nerve-conductor. When a spark was produced, contractions occurred as through a free-conductor.

Consequently, when these different problems were investigated and their results confirmed in a long series of experiments, we felt permitted not only to attribute the phenomenon of muscular contractions to electricity, bur even to consider the conditions of the experiment as certain laws by which it was bound.

Muscular contractions of this sort, then, seemed to us within certain limits to stand in a direct proportion to the strength of the spark an of the animal as well as to the length of the conductors, particularly the nerve-conductors. They seemed to stand in an inverse proportion, however, to the distances from the conductor of the electrical machine. These contractions, moreover, appeared generally stronger to us when the animal was set on the same table with the electrical machine and the table was covered with an oily coating, or when the animal was removed from the table and laid on a non-conducting, rather than a conducting substance.

I have said, to be sure, that a direct proportion seemed to me to be maintained in the contractions, bur only within certain limits. [9] It has been found, for example, that if you shorten a nerve-conductor of a length which is sufficient to bring about contractions, the contractions do not diminish, but disappear. If, however, you lengthen it, the contractions in fact grow stronger, bur only up to a certain point, beyond which-however far you extend the nerve-conductor-the contractions are augmented imperceptibly, if at all. The same can be said about other elements of the proportion I have set forth.

Now since we had observed the great capacity of a spark discharged from the conductor of an electrical machine to produce muscular motion, it seemed to us that an electric flash which resulted from the discharge of a quadratum magicumpromised even greater contractions. The experiment turned out quite differently, however, for to our astonishtnent, no movements appeared in an animal prepared in the usual way.

Now since these experiments bad been carried out with so-called positive electricity, it remained for us to undertake similar experiments with negative electricity.At first, therefore, we insulated the electrical machine and the man who turned it. We brought the frogs which were provided with their own conductors, as was necessary, dose to an iron rod which the assistant held in his hand. The frogs were set on a glass surface so that they would obtain no electricity from neighboring bodies. Then the aforementioned assistant, who was turning the machine, intentionally produced sparks from the neighboring objects with the iron rod. We saw contractions take place in the prepared frogs in the same manner as they occurred when sparks were discharged from the conductor of a non-insulated electrical machine.

In addition we experimented with negative electricity in the following manner. We set a nerve-conductor, Fig. 4, C, at a certain distance from the negative surface of a Leyden jar. Then we produced sparks, Fig. 5, from the positive surface, as the natural philosophers say, or that surface to which electricity had been given.The frogs reacted in the same way as with positive electricity. It is notable that this even occurred when the iron wire which served as a nerve-conductor was at some distance from the external surface of the jar and when it was completely enclosed by a long glass tube and the frog itself was confined in a glass receptacle. The only requirement was that the open end of the tube touch the outer surface of the aforementioned jar. These same contractions were obtained, more-over, if a spark were produced from the hook of a Leyden jar at the same time that it was being charged with electricity, as they say or a little later. [10] They also occurred if a spark were emitted either in the same place in which the jar was being charged, or elsewhere after it had been removed at a distance from the electrical machine.

These results furthermore, were obtained when the frogs were provided not only with a nerve-conductor bur also with merely a muscle-conductor. In a word all the results of this experiment with the Leyden jar approximated the corresponding experiment with the electrical machine although the prepared animal could receive no electricity from the outer surface of the jar, from nearby bodies, or from any other possible source.

Now in even another way we sought to experiment with surfaces charged with negative electricity and by producing small sparks from them, to investigate the resulting contractions. I placed a frog, prepared of course, on the upper side of a magic squareto which the electricity from the electrical machine was directed to flow. I produced a spark from the lower side when the electrical machine was at times at rest and at times in motion. Now when the electrical machine was turning, the accustomed contractions were always observable, but when it was at rest only rarely did they occur and then only immediately after the electrical machine came to rest.

After these experiments utilizing the electrical machine had been carried out, we also employed the electricity of the electrophorus, so as not to pass over any kind of electricity that produces a spark. We discharged a spark, therefore, from the plate of an electrophorus and the accustomed phenomenon of muscular contractions appeared. This occurred not at great distances, as when the spark was discharged from the conductor of the electrical machine, but only at small distances. Even at that the contractions were very slight. Although we scarcely-and not even scarcely-seemed in a position to have any doubts about the cause of the phenomenon, with so many experiments having been carried out which were concerned with the forces of electricity, nothing seemed more suitable, nevertheless, for firmly establishing the cause than to apply a very sensitive electrometer to the animalconductors.

Thus we attached a small electrometer, fashioned after the design of the renowned Volta, to the conductors. We covered one side of the straw leaves of the electrometer with very thin tin foil, that they might be more suitable for the experiment. At first, when the conductors were insulated, the leaves were frequently drawn apart from one another at the turning of the electrical machine, bur at the production of a spark, they often fell together. When the wires were freely conducting, however, the leaves did not with draw from each other at all at the turning of the electrical machine. It was only at the discharge of a spark that they gave out little jumps and vibrations, which clearly seemed to indicate some passage of electricity through the conductors of the animal when contractions were produced.

Now then to place the results of the experiment beyond all doubt, we sought in various ways to prevent the electric fluid from the electrical machine from passing (in whatever way this might be done), into the animal and its conductors. First, therefore, I enclosed the animal in a glass jar. Then I made an opening in a wall which was near the electrical machine and inserted a glass tube through the bole. (This bole penetrated the thickness of the whole wall.) I so glued the mouth of the jar to the opening in the wall that the nerve-conductor, passing through the inserted tube, bung from the opposite side of the wall in the next room. When a spark was discharged from the conductor of the electrical machine see! there were muscular movements.

I arranged the animal and its conductor, moreover, in the reverse manner: that is, the conductor was placed in the jar where the animal had been originally and the animal hung where the conductor had been at first. Then employing the same techniques, I arranged everything as before. When I produced a spark, the same movements were evident.

But although in this type of experiment every course of the electric fluid from the electrical machine seemed to have been completely blocked, nonetheless, I designed and built a little instrument, Fig. 6, which was much simpler and more convenient than the apparatus described above. This could readily be set at various distances from the electrical machine, and the animal - as well as the nerve-conductor and the muscle-conductor-could easily be placed and enclosed within it.

The design of the little instrument is as follows. It is composed of two glass jars, one of which rests upon the other. In the top jar is the nerve-conductor, which, for the sake of convenience, can be made up of the small lead shot used by hunters. In the bottom jar are the animal and similar pellets which can serve as the muscle-conductor, since the animal, set up as though it were standing on its feet, has these pellets in contact, as it were, with its muscles.

The animal is easily held in this position and is in communication with the conductor in the top jar by means of an iron wire which suspends the animal through its spinal cord. The wire is fastened in the cork stopper of the top jar and, projecting into the jar cavity, is surrounded and covered by the lead shot.

A stopper of this kind prevents the lead pellets from falling out when the top jar is inverted and is placed on the bottom one. In order that the top jar, moreover, may not be easily separated from the bottom one and that the electric fluid cannot gain access [1 2] for itself through the cracks which may exist between the openings of both jars, the mouths of the jars are joined by a certain special cement made of wax and turpentine. This is done in such a way, however, that the jars can be separated at will but can again be joined together when the occasion demands.

Now when this little instrument was placed on the same table with the electrical machine at a certain distance from its conductor, not only similar, but even more vigorous movements were seen at the discharge of a spark than when the animal and its conductors were in the open air. The muscular movements followed the laws which we mentioned above in the same proportion. After these results had been seen, I would easily have given up my original postulation that the electricity, excited in the conductor of the electrical machine, in some manner or other motivated these muscular movements through the discharge of a spark, had not the experiments which were carried out above-and the growth of a certain strong suspicion that the phenomenon certainly ought not be ascribed to the electricity on the inner surface of the jar working on the animal and its conductors at the time a spark was discharged-recalled me to my first opinion. Not only did subsequent experiments that were undertaken, but more particularly the motions of an electrometer placed inside of the little instrument, completely confirm my suspicion. For the very light shot and wires within the electrometer immediately changed position and were separated from one another when the electrical machine was turned. When the sparks were discharged, however, they were restored to their former position and resumed contact.

Now, after we had performed and thoroughly analyzed these and other experiments, it became apparent that we should also experiment on living animals in order to make our work even more useful.

So as not to kill the animals, we experimented on the crural nerve within their dissected upper thighs rather than that within their abdominal cavities. Then we proceeded to separate the nerve from the surrounding tissue, to draw it out from the muscle, and to attach it to a conductor. When a spark was discharged, the limb reacted by contractions, which seemed to be less violent, however, than those in a dead animal.

Since, in the several experiments that had been analyzed thus far, the animal, its conductor, and the machine communicated with one another through an intervening layer of air, I determined to investigate [13]what would happen when this communication was interrupted and then completely broken.

I proceeded in this way. First I placed the little instrument with its prepared animal and conductors, as in Fig. 6, under a glass jar. This was set at dose range to the electrical machine and when a spark was discharged, the customary contractions were produced.

I placed this same jar with the little instrument under another much larger jar and this under a still larger one. Again contractions occurred when a spark was discharged. The more jars there were and the greater their thickness, however, the more sluggish the movements were.

Then I prevented all communication through the layer of air between the animal and the electrical machine by setting the same little instrument with its animal under the receiver of a pneumatic pump at some distance from the conductor of the electrical ma-chine. I made an opening in the top jar so that it could be evacuated by the pump through repeated exhaustions. Sparks were discharged both when the air was being evacuated and when it was not. In either case, a parently similar contractions were produced.

After we had carried out numerous different experiments with electricity that becomes activated through a spark, we sought to discover, not without perseverance and hard work, whether this same electricity also produces its effect on muscular movement through other means. We frequently observed muscular contractions if the nerve-conductor, Fig. 3, B, were set as dose to the conductor of the electrical machine, Fig. I, C, as possible and then if the plate of an electrophorus were lifted from the resin disc, or if (when the electrcophorus had been set at a considerable distance from the aforementioned conductor) the same plate were brought very near to it, in both cases without a spark discharge.22

All the foregoing experimentation was performed on so-called cold-blooded animals. After we had made these discoveries, we were very eager to carry out the same or similar investigations also on warm-blooded animals like chickens and sheep. We engaged in these experiments and the results were substantially the same for both kinds of animals, although by necessity the preparation of the warmblooded animals was different. We first had to cut loose the crural nerve, not within the abdominal cavity, bur externally in the thigh itself. Then we separated it from the surrounding tissue, drew it out, and attached its conductor. After that a spark was discharged from the conductor of the electrical machine when the limb was either attached to the living animal or had only recently been severed from it. For otherwise, if the usual procedure for preparing frogs were followed, [14] contractions were absent, perhaps because the muscles lost their ability to contract before the long and complicated preparation could be completed.

In conclusion, there are several unusual and useful facts connected with these experiments using both kinds of animals, which, to my way of thinking, are worthy of notice and came frequently to our attention. The first is that the older the prepared animals are, the whiter their muscles, and less blood they have, the more subject they are to muscular contractions: hence this phenomenon can probably be excited more quickly, easily, and for a longer period of time in cold- than in warm-blooded animals. The former have thinner blood of a type that coagulates more slowly, and for this reason it flows much more easily from the muscles. The second is that the pre pared animals which were subjected to the electrical experiments became putrified and rotten long before those that had not been exposed to the force of the electricity. Finally the phenomena we have described occurred only if the animals had been prepared for experimentation in the manner we have mentioned above; otherwise the contractions failed to take place. For if conductors are applied and even attached to the brain or muscles rather than to the exposed spinal cord or nerves, as we have been accustomed to do, or if the nerve-conductors are further extended to the muscles, or if the nerves are improperly separated from the surrounding tissue, the resulting contractions are trifling or do not occur at all. We are convinced that most of the facts we discovered from these experiments are the result of this technique of preparing and separating the nerves.

PART II

THE EFFECTS OF ATMOSPHERIC ELECTRICITY ON MUSCULAR MOTION

Having already set forth our discoveries on the effects of artificial electricity on muscular contractions, we wanted nothing better than to investigate whether so-called atmospheric electricity produces the same phenomena or not, or more precisely whether lightning flashes like discharged sparks excite muscular contractions when the same techniques are, used.

[15] Therefore in the open air, we set up and insulated a long conductor, appropriately made of iron, Tab. 2, Fig. 7, and fastened one end of it to a high part of the house. When a thunderstorm arose we fastened the nerves of prepared frogs or the prepared limbs of warm-blooded animals to the other end, as in Tab. 4, Figs. 20, 21. Then we attached to their feet another similar conductor of the greatest possible length so that it might reach down to the water of the well represented in the diagram. As we hoped, the result completely paralleled that in the experiment with artificial electricity. Whenever lightning flashed, all the muscles simultaneously fell into numerous violent contractions. These contractions preceded and as it were gave warning of the thunder to follow, just as the flash and illumination of lightning is wont to do. Indeed, so great was the agreement of the phenomena that contractions occurred without the addition of a muscle-conductor and with an uninsulated nerve-conductor. What is more, we observed these phenomena taking place, contrary to our expectation and belief, even with the conductor attached to a lower part of the house, Tab. 2, Fig. 8, particularly if the lightning bolts were great or erupted from clouds overlying the site of the experiment or if a person held the iron wire, F, in his hands at the same time the lightning flashed.

Contractions were evident, moreover, if the animal lay in the open air, or was enclosed in an appropriate jar for the sake of convenience as in Fig. 7, or was kept within a room. They even took place when the nerve-conductor was set at some distance from the nerves themselves, especially when the lightning was very strong or near at hand. We described a similar phenomenon with artificial electricity when the sparks were particularly strong or were discharged near the animal. It is noteworthy that the entire electrical force in the lightning was nor dissipated in only one muscular contraction as with the spark, bur with many contractions following one another in turn almost simultaneously. Their number seemed to correspond to the number of peals usually given out by thunder.

Now such contractions were evident nor only when lightning flashed, bur also appeared quite spontaneously under threatening skies when clouds passed dose to the elevated nerve-conductors. When this happened, the electrometers gave out clear indications [16] of electricity and sparks frequently could be discharged from the elevated conductors themselves. With the contractions stimulated by lightning, however, sparks frequently were not discharged and even a very sensitive electrometer scarcely recorded by its movement any trace of electricity.24

Experiments of this kind were undertaken not only on dead, but also on living animals, and the phenomenon of contractions appeared in both. No experiment was omitted which we had tried with artificial electricity and the ensulng results were essentially the same. At first sight, indeed, the following difference seemed worthy of notice, namely that prepared frogs which were fitted with a conductor and were enclosed in the little glass instrument, Tab. 1, Fig. 6, set at a certain distance from the conductor of the electrical machine were violently moved, as we said, by the discharge of a spark. On the other band, when lightning flashed from the clouds, these frogs were absolutely unmoved - perhaps because the electricity was too weak, having been carried by a conductor to the little instrument from a cloud bearing an accumulation of electricity, and encompassed too small a part of the instrument's outer surface, with the result that either the electrical force was not strong enough to induce contractions or that none of it reached the little instrument. In the same way and for precisely the same reason contractions were not evident at the discharge of a spark if the little instrument were set apart from the electrical machine and placed near the end of the conductor, Tab. 1, Fig. 3, EE, which was far distant from the machine.

Inasmuch as careful investigation reveals that artificial and atmospheric electricity operate in the same way, perhaps it is necessary that the electrical atmosphereencompass the glass instrument either completely or in large part to produce the aforementioned contractions within that receptacle. From our description of the instruments position in the experiment, it is evident that this condition was not fulfilled.

We discovered, moreover, after examining the laws of the observed phenomena as well as investigating the muscular contractions, that the former were maintained similarly in experiments involving both atmospheric and artificial electricity.

Since we had observed the effects of the so-called electricity of storms, both of lightning flashes and thunderboits-we determined to test how summer evening heat lightning affects animals prepared in the usual way. Consequently we attached the same animals to our open-air conductor when the sky [17] was filled with heat flashes (as we had done previously when there was lightning. No contractions took place at all, perhaps because heat flashes of this kind either do not have their source in electricity, or if they do, they occur a great distance away and operate in a completely different manner from lightning. This is a question, however, that would be of particular interest to the natural philosophers.

PART III

THE EFFECTS OF ANIMAL ELECTRICITY ON MUSCULAR MOTlON

After we had assessed the effects of atmospheric electricity present in storms, I was extremely eager also to investigate the strength of ordinarescent electricity.

Since I had upon occasion remarked that prepared frogs, which were fastened by brass hooks in their spinal cord to an iron ralling which surrounded a certain hanging garden of my home, fell into the usual contractions nor only when lightning flashed bur even at times when the sky was quier and serene, I surmised that these contractions bad their origin in changes which occur during the day in the electricity of the atmosphere. Hence with confidence I began diligently to investigate the effects of these atmospheric changes on the muscular movements I witnessed and I repeated the experiment in various different ways. Therefore at different hours and for a span of many days I observed the animals which were appropriately arranged for this purpose, but scarcely any motion was evident in their muscles. I finally became tired of waiting in vain and began to press and squeeze the brass books which penetrated the spinal cord against the iron ralling. I hoped to see whether muscular contractions were excited by this technique and whether they revealed any change or alteration related to the electrical state of the atmosphere. As a matter of fact, I did observe frequent contractions but they had no relation to the changes in the electrical state of the atmosphere.

Now since I had observed these contractions only in the open air and had nor yet carried out the experiment elsewhere, I was on the point of postulating that such contractions result from atmospheric electricity slowly insinuating itself in the animal, accumulating there, and then being rapidly discharged when the hook comes in contact with the iron railing. For in experimenting, it is easy [18] to be deceived and to think we have seen and detected things which we wish to see and detect.

But when I brought the animal into a closed room, placed ii on an iron plate, and began to press the hook which was fastened in the spinal cord against the plate, behold!, the same contractions and movements occurred as before. I immediately repeated the experiment in different pieces with different metals and at different hours of the day. The results were the same except that the contractions varied with the metals used; that is, they were more violent with some and weaker with others. Then it occurred to me to experiment with orher substances that were either non-conductors or very poor conductors of electricity, like glass, gum, resin, stones, and dry wood. Nothing of the kind happened and no muscular contractions or movements were evident. These results surprised us greatly and led us to suspect that the electricity was inherent in the animal itself. An observation that a kind of circuit of a delicate nerve fluid is made from the nerves to the muscles when the phenomenon of contractions is produced, similar to the electric circuit which is completed in a Leyden jar, strengthened this suspicion and our surprise.

Furthermore, while I held in one hand a prepared frog with a hook fastened in its spinal cord in such a way that it stood on its feet on a silver box, with the other hand I struck the top of the box on which the frogs feet rested, or its side, using some metallic instrument. Contrary to expectation, I saw the frog react in violent contractions as often as I used this technique.

After making these observations I asked Rialpus, a Spanish scholar and one time Jesult who was enjoying a country holiday with me at the home of a most excellent and distinguished gentleman, Jacob Zambeccarus, - I asked him, I repeat, to offer a helping band in this experiment just as be had very kindly done in other experiments. I suggested that be hold the frog as I myself bad done before, not only for the sake of convenience, bur also that I might alter the method of experiment a little, while I struck the box again. Contrary to expectation, however, the contractions were absent. When I carried out the experiment alone as before, the contractions were produced once more.

This result led me to hold the animal in one hand, as I [19] had done before, and Rialpus hand in the other and to ask him either to touch or strike the box with his free hand so as to form a kind of electrical chain. To our joy and surprise, contractions immediately took place, only to disappear if we separated our hands.

They reappeared if we joined our hands once again.

Although, in fact, these results seemed sufficient to indicate an electrical flowing-out, as it were, of the nerve fluid through the human chain, nonetheless we wished absolutely to confirm so significant and novel a discovery. Thus Rialpus and I formed a chain, not by holding bands, bur through some intermediate body, now through a glass rod (a non-conductor, and again through a metal rod (a conductor). In this experiment, we discovered to our pleasure that contractions were produced when the metal rod was used, but completely disappeared with the glass rod, and that to no purpose was the box either touched or struck even with heavy blows from a conducting body when the latter was used. For this reason we thought we had established the fact that electricity of this kind stimulates contractions, in whatever wayit could bring this about.

Now, to throw further light on the problem, I had the greatest success in placing a frog on a non-conducting surface, like glass or resin, and then applying to it first a conducting arc and next one either totally or partially non-conducting. One end of the arc I attached to the book fastened in the spine; the other to the muscles of the limbs or the feet. From this experiment we see that contractions are produced with the conducting arc, Tab. 3, Fig. 9, bur that they are absent with a partially conducting and totally non-conducting arc, as in Fig. 10. In this experiment, the conducting arc consisted of iron wire and the hook was of brass.

These observations led us to the assumption that the contractions, which (as we said), were produced in frogs lying on a metal surface when the book in their spinal cord was pressed against the same surface, must be ascribed to a similar arc whose place was filled by the metal surface in some way or other. Consequently these contractions would not be excited in frogs lying on some non-conducting surface, although precisely the same techniques were employed.

A fortunate chance observation, if my judgment is correct, clearly confirmed this opinion of ours. If a frog is so held in the fingers by one leg that the book fastened in the spinal cord [20] touches a silver plate and if the other leg fails down freely on the same plate, Tab. 3, Fig. 11, the muscles are immediately contracted at the instant that this leg makes contact. There-upon the leg is raised, but soon, however, it becomes relaxed of its own accord and again falls down on the plate. As soon as contact is made, the leg is again lifted for the same reason and thus it continues alternately to be raised and lowered so that to the great astonishment and pleasure of the observer, the leg seems to function like an electric pendulum.

One can clearly see how conveniently and neatly this phenomenon can be repeated with a plate that functions as a kind of arc, producing the aforementioned circuit when the free leg falls against the plate but being unable to effect this when the leg is raised from its surface. This evidence that a metal plate functions as an arc is neither obscure nor open to doubt.

One is unable to describe, however, by what means this plate excites muscular contractions and through what innate capacity (for indeed t is capacity), frequent, vigorous, and even prolonged contractions are produced. These occur not only if the hook, fastened to the spinal cord, is pressed against or rubbed over the metal plate, but even simultaneously with the hook's merely touching the surface, and also if, once the hook has touched the plate, its contacts with it are somewhat altered-as when someone lightly strikes either the surface on which the animal lies, or the supports on which it rests. Bur so much for the kind of arc, as it were, the metal plate represents.

Before our discussion turns from the usage and capacities of the arc, we do not want to pass over the following information which is particularly apt in revealing the arc's significance, and I might say, capacity for bringing about such muscular contractions; for indeed these contractions can be produced more clearly and quickly with not only one, but with two arcs so set up and arranged that the end of one touches the muscles, and the end of the other similarly comes in contact with the nerves, while the other ends are brought in contact with one another, or if necessary, are rubbed together, Fig. 12. In this experiment, it is particularly remarkable that the electricity inducing such contractions is not appreciably dispersed or dissipated either through the contact of the hands with either arc or through repeated contacts of the arcs with the parts of the animals.

[21] We have frequently observed, more-over, that the following unusual and remarkable technique which stimulates the weakened reactions of prepared animals-namely the use of a diversity and variety of metals for the conductors of the arc or the conducting plate-is extremely effective in contributing to and augmenting muscular contractions, and without doubt is much more satisfactory than the use of one and the same metal.- For example, if the arc, the hook, and the conducting plate are all of iron, more often than not the contractions will be insignificant or completely absent. Bur if, for example, one of them is iron and the other copper, or better still, silver (for to our way of thinking, silver is the best of all metals for conducting animal electricity), contractions that are of greater and of longer duration will immediately be produced. The same thing occurs if one and the same surface of a non-conducting plate is partially covered by two different metal foils (e.g. tin foil on one part, and brass on the other). This results in much greater contractions than if the whole surface were covered or, as they say, armed by one and the same metal, even though it be silver.

From the discovery of a circuit of nerve fluid, (an electric fire, as it were,) it naturally seemed to follow that a two-fold and a dissimilar, or rather an opposite, electricity produces this phenomenon in the same way that the electricity in the Leyden jar or the magic square is two-fold, whereby it releases in these bodies its electric fluid in a circuit. For, as the natural philosophers have shown, a flow of electricity in a circuit can take place only in a restoration of equilibrium and occurs chiefly between two opposite charges. That these charges were embodied in one and the same metal seemed contrary to nature and our observations: therefore all that was left was to suppose that both were present in the animal.In order to dispense with the suspicion that in the course of my experimentation I had been able to impart electricity to the animals, I fastened a brass arc, covered with silver foil to a glass rod. I held this rod in my hands when I touched the animals with the arc. Despite these precautionary measures, contractions nevertheless took place.

Inasmuch as these experiments had been carried out in the open air, I began to wonder what would happen to the electricity of an animal if it were submerged under water. I carried this out and moved the ends of an arc in the usual way [22] so that one end touched the iron book of the spinal cord and the other the feet of the animal. The resulting contractions were similar to those produced in the open air.

The following unusual fact was revealed to me in this experiment: if I merely touched the hook in the spinal cord of the animal, sub-merged under water, with the aforementioned arc or some other conducting body, contractions were immediately produced. It seemed reasonable to ascribe this phenomenon to the water's functioning as an arc. Now, however, I submerged the animal, not in water, as previously, but in oil to see whether or not contractions occurred under these conditions. Again I applied the same conducting body to the book in the spinal cord, but no contractions were evident since oil could not substitute as a conducting arc. This result strengthened me not a little in my preconceived opinion.

After these discoveries had been duly noted it seemed quite possible to me that the twofold and opposite electricity could be found without delay in the prepared animals and that either one component bas its seat in the muscle and the other in the nerve or both are present in one or the other as the natural philosophers assert to be the case in the tourmaline stone.

I eagerly began, therefore, to seek out and investigate its seat, my initial objective being to discover what type of electricity the nerves display. I first moved a glass rod and then one of sealing-wax near the severed spinal cord of frogs which I had freshly killed in preparation for the experiment. When the former was applied, no muscular movements were visible, but they did occur with the latter, and even at a distance of four and more lines, provided that the spinal column had been encased in tin foil as we mention below. In place of the glass rod we repeatedly used the disc of the electrical machine, turning in numerous revolutions, in order to learn whether the greater supply of electricity accumulated in the disc excited muscular contractions which the rod could not do. The result, however, was the same: not the slightest movement occurred in the muscles.37

Thus we learn from these experiments that nerve-electricity is positive, since the natural philosophers demonstrate that only opposite kinds of electricity can bring about the customary effects and movements.

Then we turned to an investigation of muscle electricity. [23] We undertook the same experiments with the muscles as we had done before with the nerves but could observe no movements in the former with either the application of positive or negative electricity.

We accordingly returned to nerve electricity which reacted more favorably to our experiments, and in our investigations we used sealing wax and employed the same techniques we had used earlier when we experimented with it through the discharge of a spark. Almost the same contractions were produced, except that they, that had responded earlier to the force of the electricity in the spark, were much less intense with the sealing-wax The usefulness of the conductors, moreover, was the same, the laws were the same, and the muscular movements were clearly produced in the same proportion.

But since there seemed to be no more suitable method for detecting the seat, as it were, of both kinds of electricity than in increasing and expanding the electricity, a problem both obscure and difficult, I seriously contemplated means of doing this. First of all, I was led by analogy to cover the nerves wherein there seemed to be electricity and whose nature we had investigated, with some metal foil, preferably of tin, even as the natural philosophers were accustomed to do with their magic square and the Leyden jar, Tab. 3, Fig. 9.

Through this device in a remarkable way such forceful muscular movements developed that even without an arc contractions were produced through one single contact by a body of either a conducting or non-conducting nature when the nerves were armed, provided that the animals had been recently prepared and were still lively. This device, moreover, also greatly increased the efficacy and usefulness of the arc and other instruments, and finally brought about contractions that were extremely violent, of long duration, and essentially constant in animals (that were vigorous before dissection), even with the arc or the body removed which touched the armed nerves.

Furthermore, the power and efficacy of this device was so great in increasing the force of electricity of this kind that the circuit which had heretofore been scarcely visible when the hook and arc were used, emerged so vigorous and active that it was completed in a little frog through a chain of electricity, as it were, formed by not only two but occasionally through three or more men. The customary contractions took place even with [24] older animals whose muscles were white, especially in the summer when a storm threatened.

If the exposed brain and spinal cord in pre-pared animals, moreover, were partially covered with metal foil, strong and lively contractions resulted when the arc was applied in the usual way. without this device I had previously tried in vain to excite these contractions with an arc or a similar instrument.

After I had discovered the great efficacy of tinfoil applied to the nerves in augmenting animal electricity, I decided also to investigate the effect of this foil when used on the muscles. The contractions, however, did not seem to increase appreciably from this, but indeed, after numerous experiments we finally concluded that there was a noticeable increase of muscular movement if only the muscles, but particularly, if only the nerves or spinal cord or cerebrum were encased in tin foil. Scarcely any occurred, however, if these parts, as well as the muscles were covered simultaneously with the same tin foil and an arc were applied to the armed areas.

Not only were contractions intensified, moreover, through the metal foils enveloping the exposed spinal cord, but they were also increased when the spinal column was covered by this foil, extending not only externally on the back to the muscles but even internally in the abdominal cavity, particularly in that area from which the nerves branch out. It did not make any difference if one bad covered these parts or the nerves in particular with a large or small piece of foil, it was enough to have covered them with any foil at all and to have touched one end of an arc to this and the other to the muscles. In place of metal foil, moreover, we used with equal success an electric amalgamwhose powder we sprinkled over a nerve or applied to it in the form of paste which was made of the powder and oil. But when we used another metal powder, iron, for example, or bronze, and even employed the same technique, there was scarcely any increase of muscular motion.

Now that a method had been found where-by we could successfully increase electricity of this kind, we sought to discover its seat with greater eagerness and confidence. Consequently, since at one time we had covered the nerve, and at another the muscle with this same foil, we now detached a muscle with its corresponding nerve from the animal, lay it on a non-conducting plate, and applied the arc to it in the usual way. We followed the same procedure with the whole muscle as with it cut, covering one part of it with metal foil and then applying one end of an arc to the armed part of the muscle and the other to the bare muscle. [25] Through these investigations, however, we were unable to discover what we were seeking.

All that we discovered was that much weaker contractions were produced in the muscle with its nerve that was detached from the animal than when both had been left in their natural places in the animal. In a whole muscle, moreover, contractions which heretofore had been quite small and weak, indeed could hardly be said to take place at all. Nevertheless contractions occurred occasionally if one end of an arc were applied to the armed portion of the muscle and the other to the adjoining bare surface of the muscle. Other methods of experimentation produced no contractions. There was a similar result in the experiment with the internal substance of the muscle, but one much more difficult to carry out. If an arc were applied to an armed nerve in the same manner or if even the small end of some conducting body instead of an arc were used and partially touched the edge of metal foil and the bare nerve, contractions were produced much more easily and quickly.

We carried out these experiments to discover the seat of animal electricity but it became evident to us that this problem, which could not be sufficiently clarified by experiment, must be left primarily to conjecture. But of this we shall write later on.

We will now investigate several points we deemed worthy of further notice in our experiments with this kind of electricity. One of the first of these is that animal electricity which is stimulated by ordinary electricity, as we have indicated, at a distance of several lines, is nor activated even at the shortest distance by itself and alone; for indeed a contact is always necessary for it to produce its effect. We often see contractions, moreover, that are clearer, quicker, and stronger if the end of an arc touches the outermost edge of a metallic layer covering the nerves and muscles, than if it comes in contact with its surface. Similarly if it touches the end of a hook rather than its other parts, the contractions are stronger. From these observations, it is clear that animal electricity emulates in no small measure common and ordinary electricity which has a proclivity for seeking out and choosing angles and points.

These indications, to my mind, clearly obvious and straightforward, of the presence of an electricity in the muscles and nerves encouraged us diligently to bring to light additional facts about it. Hence, first of all in place of the aforementioned metal foil, we partially covered the nerves and muscles with a non-conducting substance, namely silk cloth completely saturated with oil in which pitch had been dissolved, [26] in order to see whether or not there would be contractions when the arc was applied. They were totally and completely absent. It was necessary to prepare and apply silk cloth in this fashion to prevent contractions from taking place inasmuch as silk cloth could not accomplish this by itself, since it was easily saturated and moistened by the conducting animal fluid, nor could oil alone do it since this liquid yielded place to the end of the arc to such a degree that the point came into complete contact with the part lying under it.

We then investigated whether electricity of this kind follows the pattern and nature of ordinary electricity in that it makes a path more easily through certain conducting bodies than through others. We saw an essential similarity between the two and remarked that the former, like the latter, makes its way more easily through metal than through wood. Of the metals, it is conducted far more easily through gold and silver and less successfully through lead and iron (especially when it is rusted). Thus if an arc or the plates functioning in place of an arc were made of metal, muscular contractions were produced more quickly if they were made of silver, or, for optimum conductivity, if they were covered with the thinnest possible silver foil, than if they had been made of lead, for example, or iron. After investigating the conducting power of solid bodies, we likewise looked into the same property of fluids, and the result was practically the same. We discovered that animal electricity makes its way most successfully through aqueous fluids but is delayed and virtually stopped by only fluids. To prove this by experiment we used small glass tubes, one end of which was plugged with some substance through which we drew a wire of silver or copper and covered with lead foil in such a way that one end was partially free within the cavity of the tube while the other was partially extended at a distance from it. Then we filled the tubes with the fluids to be used in the experiments, namely oil and water, plugged up the other ends in a similar fashion, and fitted in a metal wire as we had done before. After these preparations bad been carried out, we used these tubes with the bent metal wires either as a whole arc or as a part of an arc whose ends we applied to the animal in the usual way.

When these tubes were applied, Tab. 3, Fig. ì4, to the animal, there were no resultant contractions with the oil-filled tubes but many with those filled with water.

[27] From these experiments it seemed that nothing promised greater usefulness than a careful investigation of the conducting and non-conducting properties of the different parts of animals. Through experimentation we discovered that all parts of the dissected animals without doubt freely conducted and easily transmitted electricity of this kind, perhaps because of the moisture in which they are bathed either by nature or through dissection and preparation. For the different freshly dissected solid parts, like muscle fiber, cartilages, nerves, bones, and membranes, (having been placed on a glass plate), or the fluid parts like blood, lymph, serum, and urine, (having been enclosed in the aforementioned tubes), were fitted and attached to prepared and in particular to armed nerves, and then if one end of an arc were applied to these parts and the other end to the muscles, contractions were immediately produced, just as if the end of the arc had been applied to the nerves themselves. We discovered that the results were the same if the experiment were undertaken with the conditions reversed and if the aforementioned bodily parts of the animal were attached to the muscles rather than to the nerves, and if one end of the arc touched these parts and the other the armed nerves. We saw a different outcome, however, if the solid parts bad not been dissected recently but were dried out either naturally or artificially. What is more, contraction were produced not only when these parts were artificially arranged, but also when they were still present in the natural state within the animal or in a condition approximatìng the natural state; for if one end of an arc is applied to insulated, or better, armed nerves and the other touches any other part of the body you wish, lying intact in its natural position, which in some way responds to the muscles associated with these nerves, almost the same muscular contractions are produced as if the end of the arc were touching these muscles. To our great surprise, we have seen the same phenomenon to obtain with nerves and muscles when they first are cut apart and separated from one another and then are again joined by artificial means. For if, when frogs are prepared in the usual way and their spinal columns are covered with lead foil, and their limbs are so severed from one another that each of them remains connected only to its own corresponding nerve, and then one limb is removed at a distance from the other, Tab. 3, Fig. 15, and one end of an arc is pressed against the spinal cord and the other end against the muscles or only the foot of one limb, then the muscles of only that one limb show movement and are contracted. [28] But if, however, these same limbs are carefully joined together again in such a way that they come into mutual contact, and then an arc is applied in the same manner and is pressed against the same limb, then the muscles of both limbs show movement and are contracted. Precisely the same thing occurs when the spinal column and spinal cord are split down the middle and the two parts of the severed spinal column are separated from one another with their own corresponding nerves, but with the limbs joined together as they are naturally. The muscles of only one limb are contracted when the end of an arc touches only one of the aforementioned parts of the spinal column and the other end the corresponding limb. The muscles of both limbs contract, however, when the separated portions of the spinal cord are artificially joined together again and one end of an arc touches a limb and the other these parts that have been connected. Finally, precisely the same muscular contractions occur whether the trunk of the prepared animal is intact or whether it is cut through the middle from bottom to top, provided only that the separated portions are joined artificially and painstakingly together again and are brought into mutual contact, Tab. 3, Fig. 16.

Clearly the phenomena of these contractions cannot be sufficiently well explained unless one assumes that the internal moisture present in the bodily parts affords an entrance and passageway to the circulating animal electricity. Now can these phenomena bring any light to bear on the hitherto obscure cause and circumstances of the cooperation of the nerves? Oh! that wiser physiologists than we might investigate this sometime. But nothing seems to show the effects of this cooperation more graphically than if the crural nerves are prepared in frogs in the customary way, the spinal cord and head are left intact, and the upper limbs, likewise whole, remain in their natural position. Then when the crural nerve or the spinal column is armed and an arc partially touches the armed portion of the crural nerve and partially the corresponding limb, not only are the lower limbs contracted, but the upper limbs as well, and the eyelids and other parts of the head are moved. Because of the arc's contact, it seems that the electric nerve fluid flows in large part from its specified place in the nerves to the muscles, but partly seeks even higher places through the nerves and is carried up to the brain where it exerts its force, with the result that for some obscure reason, other muscles are excited to movement.

But still, although one can scarcely (and not even scarcely) doubt, from the confirming experiments and the arguments of analogy and reason, [29] the existence and movement of animal electricity in the nerves and muscles, or its emanation from the one, the other, or both, or its free passage through contiguous conducting bodies, and although we realize that the not inconsequential result of our experiments has been awarded us through good fortune and perseverance which revealed to us apparently among the first, the method whereby this electricity could practically be set before our eyes, and could be drawn from the animal and grasped, as it were, in the bands, nonetheless, we must confess, we did not feel the proof to be adequately demonstrated and investigated on all counts nor satisfactory to our way of thinking, unless we could also discover the mode and reason whereby these same muscular contractions might be obtained without the nerves or muscles being touched by any body in any way. For we were afraid that by chance these phenomena might be ascribed in some way to a certain mechanical irritation of the arc or the other instruments used and would not sufficiently explain, for this reason, these experiments in the light of a delicate electric fluid flowing out through the nerves and inducing muscular contractions. Thus it came to mind to investigate whether or not contractions occurred when the nerves were attached to one side of a magic square, the top, for example, and the muscles to the bottom, Tab. 4, Fig. 20, or the other way around as in Tab. 3, Fig. 13, and when one end of an arc touched one side and the other, the other at a point considerably removed from the arranged parts of the animal. For if the fluid flowing through the nerves were electric and if the contractions were stimulated by its flowing out from the nerves to the muscles, then I could easily perceive from this type of experiment that it was the same as if I brought an arc in contact with the muscles and nerves themselves, without there being any suspicion that a mechanical stimulus had been applied to them. When the experiment was performed, we saw, to our great pleasure, contractions take place. Contractions were also produced when the same technique was used if glass or resin coverings had been placed on one and the same plate as the natural philosophers are accustomed to do, provided that these coverings had been separated from one another at some distance so that the nerves lay on one of the surfaces and the muscles on the other, without an intervening conducting body to provide communication between them, Tab. 4, Fig. 18.

We observed, moreover, that contractions are produced by this technique without either the nerves or muscles being armed in the usual way with metal foil. Furthermore we noticed that they occurred even [30] if the spinal cord, for example, or the nerves, were placed in a glass container of water and the feet in another and then if each end of an arc touched the water's surface in the usual manner, Tab. 4, Fig. 19.

This afforded us the opportunity of investigating what would happen if the muscles were placed on an armed glass plate and if the spinal cord, enclosed in its own spinal column and connected to its own nerves, were set on a conducting plate and were either fitted with a book or were armed in the usual manner; further what would happen if the experiment were altered with the spinal cord placed on a glass plate, the muscles on a conducting plate, and an arc, as in the foregoing experiment, applied to the two opposite surfaces, one of which looked towards the spinal cord, and the other, towards the muscles; and finally what would result if not only the spinal cord but also the muscles were placed on one and the same armed glass plate. Truly the contractions were more sluggish and were harder to arouse when the muscles lay on the glass plate and the spinal cord on the conducting plate; they were stronger, however, when the positions of the spinal cord and muscles were reversed; and were much more powerful and of longer duration and occasionally occurred spontaneously without the use of an arc, being revived, as it were, if both the muscles and nerves were placed on the same covered glass plate. This was particularly true if the covered glass plate were lightly struck or moved. Then the bodies of the animals seemed to fall into a violent convulsion. Now if anyone compares these phenomena with those whose appearance we mentioned in the beginning when the muscles and the spinal cord were set on the same conducting plate and contractions were excited either through the pressure of the hook against this same plate or through other techniques we have indicated, be will easily perceive that the contractions at that time were very much less vigorous than when similar ones were produced on an armed glass plate. This is truly striking evidence that animal electricity is dispersed to a less degree, but is dispersed, nonetheless, through conducting bodies than is common ordinary electricity, but like ordinary electricity, however, it is checked and augmented by non-conducting bodies. This fact will appear much clearer, I believe, in the experiments which are to follow than in the preceding ones. Now, before I turned from such experiments, I wished to investigate whether these muscular contractions occurred not only when glass or resin plates were used, but even when I used highly polished marble, so as to remove the doubt often assailing me that the contractions [31] which I attributed to animal electricity, might have originated rather from the electricity of the armed glass or resin plate. Thus I armed the marble plates and carried out all the experiments on them I had performed earlier on those made of glass and resin. The results were essentially the same although the contractions were weaker, and so I was forced to employ those devices, stimulating contractions, which augmented the forces of animal electricity. Consequently I often had to cover one surface of a marble plate, or part of its surface (for it is the same if you use two plates or only one divided into parts by the coverings) with one metal, tin, for example, or silver, and the other with bronze or brass to produce contractions. Perhaps this was necessary because animal electricity, like common, ordinary electricity, is less readily checked by marble substances than by those of glass and resin.

I should not omit mentioning that if one end of an arc, made of a non-conducting material, is applied, as above, to armed plates, no contractions at all result. They are excited, however, if either this same end or some other non-conducting body is applied to armed nerves or the spinal cord, as we have already mentioned.

Since we had observed with wonder the experiment carried out on dead frogs whose nerves bad been severed, we were anxious to repeat the experiment on living animals with their nerves both whole and cut. Hence when we bad removed the surrounding tissue, had exposed and encased the crural nerve below that part of the leg corresponding to the ham of the knee, where it was completely bare, we then applied an arc in the usual way to this nerve as well as the crural muscles. Frequent contractions occurred, but only when the nerve was severed and armed and lay on an armed glass plate and the arc applied either to the nerve or simply to the plate and the muscles in the same way as before. Contractions were either completely or in large measure non-existent, however, if the plate on which the nerve rested was of a conducting substance and had not been insulated in any way. All of this seems to establish the postulation that animal electricity operates in essentially the same way in living as in dead animals.

Since we had observed so many and, in my opinion, clear demonstrations of the forces of animal electricity, I wished to ascertain whether the customary preparation of the nerves and their careful separation from [32] the surrounding tissue contributed to the collection and revelation of its powers, as we have indicated to be the case with ordinary external electricity. I found, indeed, that this procedure contributes a great deal. For if the brain or the spinal cord were covered with its own tin foil, when only the cranium or the spinal column had been opened and the rest of the animal was intact, and then one end of an arc were applied to an armed portion and the other to a limb, some contractions resulted in the upper limbs, but none, or very few, occurred in the lower limbs. Gradually, however, and little by little, other contractions were produced, according to the extent that the nerves were separated from the surrounding tissue, (once the animal had been skinned and eviscerated), until finally, when the nerves were completely separated and free from the tissue and were encompassed only by air, then great and vigorous contractions arose at the time that the same arc was applied with the same technique. This seems to establish that some access and passageway perhaps lies open to animal electricity from the nerves to the contiguous parts, either through moisture or through the lymph or blood vessels interlaced with the nerves. When the nerves, once severed, are free and insulated, the electricity, ready for movement, and flowing either in its entirety or in large part to the armed part of the body, completes its own circuit through the muscles and nerves with the help of an arc and induces contractions that are much greater than before a preparation of this kind is made.

A phenomenon such as this seems to furnish a new and potent argument for animal electricity; and from it perhaps one can postulate that the acceleration of blood and the circulation of fluids in muscular movement depends partially or completely on electricity flowing from the nerves to the vessels and stirring up their fluids. Certainly if room could be given to conjecture, one might perhaps give some kind of explanation as to why in old people, in whom many vessels coalesce, electricity copiously pours directly to the brain through the nerves and frequently damages it seriously, thus rendering old age even more subject to paralysis, apoplexy, and other illnesses of this kind. But of this, more anon.

Nothing seemed to us more helpful in increasing the usefulness of our experiments than diligently to repeat on warm-blooded animals the investigations tried up until now only on those that were cold-blooded.

Indeed I readily realized that if the information I had disclosed pertained only to cold-blooded animals, I had merely uncovered particular attributes of these animals which bad little general usefulness: [33] but if this could also be applied to warm-blooded animals, I had high hopes that I might be in some degree successful, if not in explaining lucidly the character and nature of muscle and nerve operation, at least in presenting it more clearly. This could not fail to bring increased benefits to physiology and medicine. After experiments had been carried out not once, but repeatedly birds and quadrupeds, notable contractions not only occurred as we hoped and as they had already done with cold-blooded animals (frogs and tortoises, in particular), bur they were produced even more easily and appeared much more clearly. It was possible to observe this peculiarity in a living animal, a lamb,41 for example. When the crural nerve had been cut and covered with metal foil and was laid out on an armed glass plate, contractions were produced merely through the contact of some conducting body with the same plate and without the application of an arc. On the other hand, when the nerve was extended on a metal plate, no contractions were excited without an arc's being applied to the animal in the usual way.

Now how can it be more appropriately or definitely demonstrated that animal electricity flows from the nerves to neighboring bodies and like common, ordinary electricity, is collected by non-conducting substances and is dispersed by conducting substances ? These are facts we have discovered through experimentation.

In conclusion, we wish the reader to bear in mind how many qualities the animal electricity weave discovered bas in common with ordinary electricity, and in particular, how similar they are in their variability, diversity, and renewability after a certain time. For the contractions produced particularly in the last group of experiments differed from one another not only in the different varieties of animals used, but in the varied nature, age, condition, and strength of each specimen. This resulted in very prompt and vigorous contractions in some, and weak ones that were difficult to detect in others. They differed, moreover, in accordance with the various seasons of the year and especially with atmospheric conditions.

In warm weather when lightning threatened, the contractions were usually greater and appeared more readily than in winter under a clear sky, although at that time, we observed that the force stimulating them was extinguished more quickly; likewise that greater and prompter contractions occurred in an older than in a younger animal, in more vigorous than in sluggish animals, and finally in bloodless, colorless muscles more readily than in those that were red and filled with blood.

[34] In one and the same prepared animal, moreover, now the contractions are trifling, now great, and occasionally even non existent; sometimes they occur in the early experiments and occasionally only after repeated attempts.

This great variety of effects or contractions furthermore is revealed after long, as well as short intervals of time.

Finally weak contractions are occasionally strengthened spontaneously and grow vigorous after a certain period of rest. When they fall, they apparently are restored through their own powers, although other external causes and circumstances scarcely, and not even scarcely, so it seems, have been changed. In just such a way ordinary electricity, dissipated through repeated experiments of the magic square or Leyden jar, seems to be restored and renewed through rest and inactivity.